This invention relates generally to bridges and abutments for use in conjunction therewith. More specifically, the invention relates to a bridge abutment in which the end of the bridge deck is directly supported by a mass of internally stabilized earth.
In the past, bridges spanning a distance between spaced apart bridge abutments have been constructed with load-bearing columns or generally vertical load-bearing walls which vertically support the weight of the bridge deck which extends between the spaced abutments. Typically, such abutments are fabricated from poured concrete and are supported by a suitable footer. Depending on soil characteristics and conditions, it is sometimes necessary to provide a plurality of generally vertical pilings which are driven into the ground to support the footers. Often, side walls or wing walls are provided for the bridge abutment and these walls are frequently fabricated from poured concrete.
The poured concrete method requires accurate placement and positioning of suitable forms to hold concrete while it cures and develops the necessary strength. Moreover, the poured concrete bridge abutments generally require a framework of reinforcing steel which must be assembled at the job site and properly positioned in the forms by workmen.
With abutments poured and cured, a bridge deck is placed spanning the distance between the spaced apart abutments. Concurrently or subsequently, an area defined between each abutment wall and the associated wing walls is filled with earth or other suitable aggregate and compacted to provide an approach to the bridge deck which conforms with the elevation existing at the end thereof.
There are other common bridge abutment constructions that utilize a combination of steel filings and concrete. These structures are complex and difficult to construct. Consequently, they are expensive.
Another design aspect relates to the physical dimensions of some bridge abutments. As the abutments become wider, it becomes necessary to form the bridge abutments in piecewise fashion to accommodate differential thermal expansion thereby introducing substantial time delays and substantially increasing the construction expense. Moreover, wide abutments are more susceptible to differential settling of horizontally spaced portions which settling may induce formation of cracks and other structural anomalies.
It is well known that the excavation and site preparation for a bridge abutment are both expensive and time consuming. In view of the above discussion, it should be apparent that the construction of footers and load-bearing walls is both very expensive and very time consuming.